The long term goal of this collaborative program between the School of Dental Medicine and the School of Engineering and Applied Sciences is the development of a new methodology for the in situ determination and quantification of chemical components of the oral environment and their relationship to metabolic processes involved in disease prevention and therapy. The purpose of this grant application is to develop microsensors and telemetric electronics for the in vivo measurement of pH and calcium ion in plaque at multiple interproximal sites of the maxillary and mandibular arches. Plaque pH and calcium have been selected in this initial proposal because their quantification is critical in understanding enamel demineralization calculus deposition and other fundamental biochemical processes in the oral environment. The study will be conducted in two phases. Phase One will include development and refinement of the pH and calcium sensors and the telemetric package; incorporation of the sensors and telemetry unit into Hawley appliances; and in vitro testing to determine accuracy and stability. In Phase Two, end stage devices will be fabricated and in vivo studies will be conducted to evaluate design features (acceptability, durability and safety) and to standardize measurements for monitoring plaque metabolism. There is no current methodology for continuous monitoring of plaque pH at multiple sites in the mouth. Further, there is no existing technology for determination of plaque ionic calcium in situ. The development and testing of these microsensors will make a significant contribution to the basic knowledge of oral biochemistry and to clinical investigations of caries, calculus and periodontal disease. This application is a resubmission of a prior approved application, and reflects additional progress in pilot development of prototype sensors and refinements of protocols for clinical evaluations.